We want user records to be extensible, hence we shouldn't complain about
fields we can't parse. In particular we want them to be extensible for
our own future extensions.
Some code already turned the permissive flag when parsing the JSON data,
but most did not. Fix that. A few select cases remain where the bit is
not set: where we just gnerated the JSON data ourselves, and thus can be
reasonably sure that if we can't parse it it's our immediate programming
error and not just us processing a user record from some other tool or a
newer version of ourselves.
This new option does three things for a host user specified via
--bind-user=:
1. Bind mount the home directory from the host directory into
/run/host/home/<username>
2. Install an additional user namepace UID/GID mapping mapping the host
UID/GID of the host user to an unused one from the container in the range
60514…60577.
3. Synthesize a user/group record for the user/group under the same name
as on the host, with minimized information, and the UID/GID set to
the mapped UID/GID. This data is written to /run/host/userdb/ where
nss-system will pick it up.
This should make sharing users and home directories from host into the
container pretty seamless, under some conditions:
1. User namespacing must be used.
2. The host UID/GID of the user/group cannot be in the range assigned to
the container (kernel already refuses this, as this would mean two
host UIDs/GIDs might end up being mapped to the same continer
UID/GID.
3. There's a free UID/GID in the aforementioned range in the container,
and the name of the user/group is not used in the container.
4. Container payload is new enough to include an nss-systemd version
that picks up records from /run/host/userdb/
We recently started making more use of malloc_usable_size() and rely on
it (see the string_erase() story). Given that we don't really support
sytems where malloc_usable_size() cannot be trusted beyond statistics
anyway, let's go fully in and rework GREEDY_REALLOC() on top of it:
instead of passing around and maintaining the currenly allocated size
everywhere, let's just derive it automatically from
malloc_usable_size().
I am mostly after this for the simplicity this brings. It also brings
minor efficiency improvements I guess, but things become so much nicer
to look at if we can avoid these allocation size variables everywhere.
Note that the malloc_usable_size() man page says relying on it wasn't
"good programming practice", but I think it does this for reasons that
don't apply here: the greedy realloc logic specifically doesn't rely on
the returned extra size, beyond the fact that it is equal or larger than
what was requested.
(This commit was supposed to be a quick patch btw, but apparently we use
the greedy realloc stuff quite a bit across the codebase, so this ends
up touching *a*lot* of code.)
In the change set 6c045a9998 the error
text for the old flag `--private-users-chown` was repurposed for the
new flag `--private-users-ownership=own` and while doing so the word
`may` was dropped leading to a grammatically incorrect error text.
This adds a two new values to --private-users-ownership=: "map" and
"auto".
"map" exposes the kernel 5.12 idmap feature pretty much 1:1. It fails if
the kernel or used file system doesn't support ID mapping.
"auto" is a bit smarter: if we can make ID mapping work, we'll use it,
otherwise revert back to classic chown()ing. We'll also use chown()ing
if we detect that an image is already ID shifted, both to increase
compatibility with the status quo ante, and to simplify our codepaths,
since the mappings become a lot simpler if we only have to map from zero
to something else, instead of from anything to anything else.
The short -U switch, and --private-users=pick will now imply
--private-users-ownership=auto instead of
--private-users-ownership=chown, since the new logic should be the much
better choice.
This replaces --private-user-chown by an enum value
--private-user-ownership=off|chown. Changes otherwise very little.
This is mostly preparation for a follow-up commit adding a new "map"
mode, using kernel 5.12 UID mapping mounts.
Note that this does alter codeflow a bit: the new enum already knows
three different values instead of the old true/false pair. Besides "off"
and "chown" it knows -EINVAL, i.e. whenever the value wsn't set
explicitly. This value is changed to "off" or "chown" before use, thus
retaining compat to the status quo before, except it won't override
explicit configuration anymore. Thus, if you explicitly request
--private-user=pick you can now combine it wiht an explicit
--private-user-ownership=off if you like, which will give you a
container that runs under its own UID set, but the files will be owned
by the original image. Makes not much sense besids maybe debugging, but
if requested explicitly I think it's OK to implement.
userns identity 1:1 mapping is a pretty useful concept since it isolates
capability sets between containers and hosts, even if it doesn't map
any uid ranges. Let's support it with an explicit concept.
(Note that this is identical to --private-users=0:65536 (which in turn
is identical to --private-users=0), but I think it makes to emphasize
this concept as a high-level one that makes sense to support.)
It's not going to be efficient if called in inner loops, but it's oh so
handy, and we have some code that does this:
asprintf(&p, "%s…", b, …);
free(b);
b = TAKE_PTR(p);
which can now be replaced by the quicker and easier to read:
strextendf(&p, "…", …);
Let's enable this in all tools that intend to write to the OS images.
It's not conditionalized for now, as there already is conditionalization
in the existance or absence of the flag in the GPT partition table (and
it's opt-in), hence it should be OK to just enable this by default for
now if the flag is set.
This tries to shorten the race of device reuse a bit more: let's ignore
udev database entries that are older than the time where we started to
use a loopback device.
This doesn't fix the whole loopback device raciness mess, but it makes
the race window a bit shorter.
Let's drop all monitor uevent that were enqueued before we actually
started setting up the device.
This doesn't fix the race, but it makes the race window smaller: since
we cannot determine the uevent seqnum and the loopback attachment
atomically, there's a tiny window where uevents might be generated by
the device which we mistake for being associated with out use of the
loopback device.
Previously, the flag did two things at once: enable support for using
generic partitions as root fs if there were only one/allow use of
partition-table-less images as root fs. And secondly, insist that there
was a rootfs, and fail if not. Let's split these two in two separate
options so that they can be used independently of each other.
There are cases where one wants to use one without the other (i.e. when
inspecting things with systemd-dissect tool it should be OK to do so
even if image has no root fs), and it's cleaner anyway.
Let's make use of the new dissection in all tools where this makes
sense, which are all tools that dissect images, except for those which
inherently operate on state/configuraiton and thus where an image
without state nor configuration is useless (e.g.
systemd-tmpfiles/systemd-firstboot/… --image= switch).
Prompted by https://bugzilla.redhat.com/show_bug.cgi?id=1930875 in which
I had previously used json_dispatch_unsigned and passed a return variable of
type unsigned when json_dispatch_unsigned writes a uintmax_t.
Clean up ignore_signals() + default_signals() + sigaction_many() a bit:
make it unnecessary to explicitly terminate the signal list with -1.
Merge all three calls into a single function that is just called with
slightly different parameters. And eliminate an unnecessary extra
iteration in its inner for() loop.
No change in behaviour.
As suggested in https://github.com/systemd/systemd/pull/11484#issuecomment-775288617.
This does not touch anything exposed in src/systemd. Changing the defines there
would be a compatibility break.
Note that tests are broken after this commit. They will be fixed in the next one.
The old name originates when this was used to discover "machine" images,
as managed by machined/machinectl. But nowadays this is also used by
portable services and system extensions, hence let's use a more generic
name for this API. Taking inspiration from "dissect-image.[ch]", let's call
this "discover-image.[ch]".
This is pure renaming, no other changes.
I think this formatting was originally used because it simplified
adding new options to the help messages. However, these days, most
tools their help message end with "\nSee the %s for details.\n" so
the final line almost never has to be edited which eliminates the
benefit of the custom formatting used for printf() help messages.
Let's make things more consistent and use the same formatting for
printf() help messages that we use everywhere else.
Prompted by https://github.com/systemd/systemd/pull/18355#discussion_r567241580
Even though many of those scripts are very simple, it is easier to include
the header than to try to say whether each of those files is trivial enough
not to require one.
Apparently SELinux inserts control data into AF_UNIX datagrams where we
don't expect it, thus miscalculating the control data. This looks like
something to fix in SELinux, but we still should handle this gracefully
and just drop the offending datagram and continue.
recvmsg_safe() actually already drops the datagram, it's just a matter
of actually ignoring EXFULL (which it generates if control data is too
large) in the right places.
This does this wherever an AF_UNIX/SOCK_DGRAM socket is used with
recvmsg_safe() that is not just internal communication.
Fixes: #17795
Follow-up for: 3691bcf3c5
This is inline with the OCI runtime spec:
On POSIX platforms, path is either an absolute path or a relative path
to the bundle. For example, with a bundle at /to/bundle and a root
filesystem at /to/bundle/rootfs, the path value can be either
/to/bundle/rootfs or rootfs. The value SHOULD be the conventional
rootfs.
(https://github.com/opencontainers/runtime-spec/blob/master/config.md)
Lennart Poettering
Yu Watanabe
Olle Lundberg
Zbigniew Jędrzejewski-Szmek
Xℹ Ruoyao
Anita Zhang
Daan De Meyer
Florian Westphal
Arian van Putten